But the true amount of money set aside for affordable housing could be significantly higher, with many councils either ignoring or refusing to give the data requested under the Freedom of Information Act.

Cornwall, Wiltshire, Liverpool, Shropshire and Doncaster councils were among 66 authorities not to give the information requested, while 267 did provide the data.

The revelation of the pot of money sitting unspent led Downing Street to claim the current system is not working properly and pledged reform.

The money is hoovered up by councils under a piece of planning law called Section 106 agreements, which sees developers hand over cash as part of planning permission being granted.

The cash has to be used for specific tasks, such as affordable housing, highways repairs and even public art.

James Prestwich, Head of Policy at the housing associations lobby group the National Housing Federation told HuffPost UK: “We understand that Freedom of Information requests can sometimes be difficult to process quickly, but we would encourage any local authorities that have not published this data to do so as soon as possible.

“They should also have a clear plan in place to spend any unallocated funding – by working in partnership with local housing associations, councils can ensure this money is being spent effectively and in a way that makes a real difference to people’s lives.”

Homeless charity Shelter also called for more transparency, with its chief executive Polly Neate telling HuffPost UK: “Councils should explain to the public why money for affordable housing isn’t being invested for that purpose given the housing emergency we face.

“But councils can’t do it on their own. The government needs to pull its weight too by making sure upcoming changes to planning rules make it harder for developers to wriggle out of building affordable homes.”

Downing Street confirmed the Government wants to see changes to the current system, where developers can escape their obligations to build affordable housing by handing over cash to councils.

A spokesperson said: “The current system of developer contributions is not working as it should.

“That’s exactly why we have proposed reforms that will support swifter development, and make the process more transparent and accountable .”

HuffPost UK’s investigation was welcomed by Twitter users, with many expressing concern that so much money was yet to be used.

great scoop from @owenjbennett. More evidence that section 106 agreements are pretty much making the housing crisis worse - they allow councils to put off actually investing in affordable housing, apparently indefinitely https://t.co/e8WZpdS4wQ